Hydrocarbons such as oil, natural gas, or the like can be obtained from a subterranean geologic formation by drilling a wellbore which penetrates the geologic formation providing a partial flowpath for the hydrocarbon to the Earth's surface. In order for the hydrocarbon to flow from the geologic formation to the wellbore there must be a sufficiently unimpeded flow path.
FIG. 1 generally illustrates a conventional hydraulic fracturing process (1). Hydraulic fracturing (also often referred to as “hydrofracking”, “waterfrac”, “fracking” or “fracing”) can improve the productivity of a geologic formation (2) surrounding a wellbore (3) by inducing fractures or extending existing fractures through which geologic formation fluids (4) such as hydrocarbon fluids, oil, gas, or the like, can flow toward the wellbore (3). Typically, hydraulic fracturing is accomplished by injecting a hydraulic fracturing fluid (5) through the wellbore (3) into the subterranean geologic formation (2) from one or more hydraulic fracturing pumps (6) at a flow rate that exceeds the filtration rate into the geologic formation (2) thereby increasing hydraulic pressure at the face of the geologic formation. When the hydraulic pressure increases sufficiently the rock or strata of the geologic formation (2) can fracture or crack. The induced cracks and fractures may then make the geologic formation (2) more porous releasing geologic formation fluids (4) such as oil, gas, or the like, that would be otherwise remain trapped in the geologic formation (2).
Generally, conventional hydraulic fracturing processes (1) include a hydration unit (9) to admix an amount of water (7) obtained from a water source (8) with one or more hydratable materials (10) including for example: a guar such as phytogeneous polysaccharide, guar derivatives such as hydroxypropyl guar, carboxymethylhydroxypropyl guar, or the like. Other polymers can also be used to increase the viscosity of the hydraulic fracturing fluid (5). Cross-linking agents can also be used to generate larger molecular structures which can further increase viscosity of the hydraulic fracturing fluid (5). Common crosslinking agents for guar include for example: boron, titanium, zirconium, and aluminum.
Proppants (11) can be further admixed into the hydraulic fracturing fluid (5) by use of a blender (12) and injected into the wellbore (3) as part of the conventional hydraulic fracturing process (1). The proppant (11) can form a porous bed, permeable by geologic formation fluids (4), such as oil or gas, that resists fracture closure and maintains separation of fracture faces after hydraulic fracturing of the geologic formation (2). Common proppants (11) include, but are not limited to, quartz sands; aluminosilicate ceramic, sintered bauxite, and silicate ceramic beads; various materials coated with various organic resins; walnut shells, glass beads, and organic composites.
Typically, conventional hydraulic fracturing processes (1) heat the amount of water (7) from ambient temperature to at least 40 degrees Fahrenheit (“° F.”) in the preparation of hydraulic fracturing fluids (5) within a closed system heater (13) in which the amount of water (7) is periodically contained, such as a boiler, or flowed within, such as pipes. Because conventional systems utilize a closed system heating unit (13), the amount of water (7) can be superheated (to about 240° F.) and then mixed with an amount of water (7) at ambient temperature by use of a mixing unit (14) including at least one mixing pump (15) and a mixing valve (16). The amount of water (7) delivered from the closed system heater (13) can then be stored in one or more storage tanks (17). The term “ambient temperature” as used in this description means the temperature of the amount of water (20) received by the heating apparatus (21).
Even though a wide variety of conventional hydraulic fracturing processes (1) exist, there remain longstanding unresolved limitations common to their use. First, the efficiency of conventional closed system heater units (13) can be about 60%. For example, for each 35,000,000 British Thermal Units (“BTU”) only about 21,000,000 BTU contribute to thermal gain increasing the temperature of the amount of water (7). The remaining 14,000,000 BTU are lost to the surrounding environment.
Second, a single conventional heater unit (13) cannot generate an amount of water (7) at flow rates or temperatures for delivery directly to the one or more fracturing pumps (6) for hydraulic fracturing of a geologic formation (2) surrounding a wellbore (3). Conventional heater units (13) which include a boiler periodically retain, heat and discharge an amount of water (7), a heated flow of water for injection into a wellbore (3) for hydraulic fracturing can only be continuous from a boiler type of conventional heater unit (13) when an amount of water (7) is being heated in one or more heater units (13) and an amount of water (7) is being discharged from another one or more heater units (13). Alternately, in conventional heater units (13) in which an amount of water (7) flows through a plurality of heated conduits, the amount of water (7) can have a relatively low flow rate (typically less than 400 gallons per minute). As a result, the conventional wisdom is to use one or combination of remedies: use additional conventional heater units (13), use one or more storage tanks (17) in which an amount of water (7) previously heated can be stored, or use an amount of water (7) superheated in a conventional heater unit (13) mixed with an amount of water (7) at ambient temperature. All of these remedies necessitate additional equipment and persons to operate the additional equipment at substantial cost.
The instant invention provides an inventive geologic formation hydraulic fracturing system substantially different from conventional hydraulic fracturing procedures to address the above described disadvantages.